What is the mass of a car that has a speed of 30 m/s and a momentum of 45,000 kg, m/s

                                                   Momentum = (mass) x (speed)

Divide each side by (speed):      Mass = (momentum) / speed

                                                   Mass = (45,000 kg-m/s) / (30 m/s) =

                                                                   1,500 kg .

Wooden , walls ,doors ,support

Letter a, because when there are unlike charges they will always attract to each other.